#define  _CRT_SECURE_NO_WARNINGS


#include<stdio.h>

int main()
{
	int n = 0, i = 0, arr[50] = { 0 };
	scanf("%d", &n);
	arr[0] = arr[1] = 1;
	for (i = 2; i < n; i++)
	{
		arr[i] = arr[i - 1] + arr[i - 2];
	}
	printf("%d\n", arr[n - 1]);

	return 0;
}